1. Field of the Invention
The present invention relates to a disk cartridge particularly suitable as an HS cartridge for accommodating an HS disk for use for example in a high density MO disk drive system. More particularly, the present invention relates to a shell capable of accommodating a disk-shaped recording medium such as an HS disk in a freely rotatable fashion.
2. Description of the Related Art
Recently, an HS disk having a greater storage capacity than an MO disk and suitable as a high density magneto-optic disk for use in a high density magneto-optic disk system (often referred to simply as an HS) has been developed. An HS cartridge has also been proposed which serves as a high density disk cartridge for accommodating an HS disk in a freely rotatable fashion in a shell composed of upper and lower shells injection-molded with a synthetic resin. The HS disk has a diameter of about 3.5 inches (85-90 mm) and the HS cartridge has a size similar to that of a 3.5 inch floppy disk cartridge.
The HS cartridge has a pair of right and left incorrect-insertion detection cut-away portions formed in the front sides on the right and left sides of the lower shell wherein the "front side" refers to the side which faces the HS drive when it is inserted into the HS drive. The upper parts of the pair of right and left incorrect-insertion detection cut-away portions are covered with a pair of right and left wings disposed in the front sides on the right and left sides of the upper shell.
When and only when the HS cartridge is correctly inserted into a cartridge holder of an HS drive, a pair of right and left incorrect-insertion preventing projections formed in the cartridge holder can be fitted into the pair of right and left incorrect-insertion detection cut-away portions thereby ensuring that the HS cartridge is correctly inserted in the cartridge holder. If the HS cartridge is tried to be inserted into the HS drive in a wrong way (as in the case where the rear end of the HS cartridge faces the HS drive or as in the case where the upper side of the HS cartridge faces down) or a wrong cartridge such as a 3.5 inch floppy disk cartridge which is similar to but different from the HS cartridge is inserted, the insertion is prevented by the pair of right and left incorrect-insertion preventing projections.
When upper and lower shells of an HS cartridge are formed by means of injection molding with a synthesis resin, it is desirable that the thicknesses of the majority of roof and bottom walls of shells be as small as possible to reduce the overall shell thickness while maintaining the thickness of a pair of right and left wings of the upper shell at a great value to achieve a sufficiently great mechanical strength. However, if the thickness of the pair of right and left wings is greater than the thickness of the majority of the roof wall of the upper shell, deficiency of synthesis resin in the pair of right and left wings occurs during the molding process, which results in formation of hollows or other deformations at the surface of the wings of the upper shell. As a result, the appearance becomes very poor and the commercial value becomes very low.